This invention relates to lifting jacks used for automobiles and other vehicles and, in particular, relates to an extension arm to operate a jack. In another aspect, the invention relates to a novel fastener which may be used to connect longitudinally tubular sections and the like.
In the vehicle industry it is common to provide a portable jack to be stored in a vehicle to enable an operator in emergency situations to lift the vehicle to effect minor repairs, for example, to change a tire on the vehicle. There are many different types of jacks available but many, if not most, are driven either by a lever or a crank which in turn drive gears and/or screws in the jack to obtain a sufficient mechanical advantage to enable the operator to lift a vehicle.
In operation a jack is located under the portion of the vehicle to be lifted and braced against the nearest solid member which will bear the weight. Sometimes, however, particularly with trucks, a jack must be located far under the vehicle or in other positions where it would be awkward or even dangerous to be near the jack while it is being operated. Accordingly, it has become common in the industry to provide an extension arm to permit the operator to operate the jack at a distance. In order to facilitate storage Of the portable jack in the vehicle, such extension arms are often broken down into several similar sections which link together end to end when the jack is needed.
One known type of extension arm consists of a number of sections of round tubing. Each end of each section is formed square or rectangular to transmit torque. One end of each section has a larger cross section than the other end so that a smaller end of one section fits snugly into a larger end of an adjoining section. The squared ends allow the joined sections to transmit torque from one to another. A set screw is provided in each of the large ends to secure or to release the smaller end of the adjoining section. In some embodiments, an indentation or hole may be provided in the smaller end to receive the set screw to effect a more secure linkage. In some other embodiments, a winged flange is provided on the head of the set screw to facilitate turning without tools.
The above construction provides the advantage of positive locking of the tubular sections as they are linked. Positive locking permits the operator not only to operate the jack but also to push and pull the jack with the extension arm with confidence that the linkage will not separate. This feature is important because the operator may wish to position the jack under the vehicle by pushing, pulling and adjusting it with the extension arm.
The construction has certain disadvantages however. Tapping a hole in the larger ends and the provision of set screws increases manufacturing costs. In embodiments without a winged flange on the set screw, a tool is required to tighten it. Assembly and disassembly of the linkage with the set screw is more difficult than other types of arms described below. The set screws can be lost, bent or otherwise damaged since they project from the sides of the sections.
Another jack extension arm known in the prior art is made from solid round bars. The bars are linked by means of a sleeve welded to one end of each bar to project a short distance beyond the end. A hole is drilled through the portion of the sleeve projecting beyond the end of the bar. At the other end of each such bar, a side hole provides a well for a press stacked spring and a ball arrangement. Upon linkage of the bars, the sleeve at one end of a bar is fitted over the end of another bar having the steel ball and spring arrangement. The ball press fits into the hole of the sleeve and fastens the sections together.
The press fit spring, ball and sleeve construction provides ease of assembly since the sections snap fit together. It also has the advantage of easy disassembly since the sections may be simply pulled apart. Sufficient tension on the bars forces the sleeve over the ball and pushes it back into the hole whereupon the bars separate. The construction has disadvantages. A solid bar is required to hold the spring and ball assembly and, accordingly, the overall unit is heavier. Further the manufacturing costs of this construction are higher than the present invention. Finally, the advantage of the ease of assembly of the snap fit connection is offset by the disadvantage that the extension arm may pull apart if the operator pulls on it to adjust or remove the jack.
Another extension arm construction known in the industry has round tubes with hexagonal ends welded on one end of each tube to reinforce it to receive the other end of an adjoining tube in a telescoping fit. Two holes are drilled completely through each sleeve and its underlying tube. Another hole is provided in the opposite end of each tube. A wire clip is then provided in the hole through the sleeve and the tube. The ends of the wire are bent to secure it in position. When an adjoining tube is fitted into the receiving end the holes align over one another. The free end of the wire clip is inserted in the aligned holes to lock the two sections together.
This wire clip construction has advantages in that it uses light tubular sections and it is simple to manufacture. It is also reasonably easy to assemble and disassemble. It provides a positive locking assembly that tolerates pulling. It has disadvantages in that the wire clip is not as neat a fastening device as the ball lock and is not as easy to use. Further the projecting wire clip is subject to being damaged or bent when it is stored in the vehicle.
It is an object of the present invention to provide an novel extension arm for a vehicle jack, which provides economical manufacturing costs, a positive lock, ease of assembly and a neat package and to provide a novel fastener for connection of hollow sections.
The invention is a member having a series of interlocking sections. It is not necessary that all sections are identical. It is, however, desirable that sections are identical to others because then the sections are interchangeable. Some sections may have an end that is different from the first and second ends described below to enable the section to link to other parts such as a jack. In view of these possible different embodiments, the invention is described in terms of first and second ends which are abutting ends of two adjacent sections. It will be appreciated that in identical sections the first and second ends will also be opposite ends of each section.
In the member of interlocking sections of this invention each first end of a section fits within a second end of another section. A first hole in each first end aligns with a second hole in each second end when one section is fitted into another section. The sections are linked in a positive lock by a fastener comprising one or more resilient legs, a stop and a lug. Each fastener snap fits within a first end of a section, with the resilient leg(s) biasing the lug to project through and beyond the first hole to an extent limited by the stop. Upon assembly of one section with another section, the lug projecting from the first hole of one section snap fits into the second hole of the other section to lock the sections together until the lug is depressed to release the second end for disassembly.
The sections are typically hollow elongated sections but it will be understood that other sections will be useful if the fastener can be inserted into a hollow end portion.
The resilient leg(s) of the fastener may press against an inner wall of the first end to bias the lug out through and beyond the first hole. The fastener preferably has two resilient legs splayed apart for stability. The resilient legs splay apart against an inner wall of a first end opposite a first hole to bias the lug out through and beyond the first hole. The lug preferably has vertical sides which act against the perimeter edge of a second hole of another section to lock the sections together. The stop acts against an inner wall about the first hole to limit the projection of the lug beyond the first hole to approximately one additional wall thickness so as to project slightly beyond the second hole after assembly. Preferably the stop is a base or stage upon which the lug is erected and from which the leg(s) depend.
In a member used for turning, such as an extension arm for a screw jack, each first end and second end will have at least one straight side to key the sections to transmit torque. Preferably the ends will be square, rectangular or other common geometric shapes known for the transmission of torque.
The assembly of the sections of the member is further facilitated by a dimple on the outermost of each second end of each section. The outwardly bent dimple rides over and presses inwardly the lug projecting from a first hole in another section as the second end is fitted over the first end.
It will be apparent to those skilled in the art that the sectional member of this invention is suitable for an extension arm of a jack.